1. Field of the Invention
The present invention relates to a screw-driving tool, and more particularly to a screw-feeding device for a screw-driving tool.
2. Description of the Prior Arts
With reference to FIGS. 1 and 2, a conventional screw-feeding device for a screw-driving tool is shown and includes a housing 10 and a belt carrier 11 disposed in the housing 10. The belt carrier 11 is provided on its outer periphery with a plurality of teeth 111 which are used to carry the strip screws 15. A unidirectional bearing 12 is disposed in the belt carrier 11 and rotated by a guide rod 13, and the unidirectional bearing 12 serves to rotate the belt carrier 11 so that the strip screws 15 can be fed automatically. At each time the belt carrier 11 is rotated a full stroke angle by the unidirectional bearing 12, the arc end 141 of the elastic piece 14 will engage in the notch 112, so that thee belt carrier 11 is positioned and the screws can be screwed into the object. Due to the unidirectional bearing 12, the belt carrier 11 only can rotate unidirectionally, and thus, the screws can be fed automatically. However, this conventional screw-feeding device still has some defects:
First, if the guide rod 13 is unable to rotate a full stroke angle due to the screw-feeding device is being used improperly, since the belt carrier 11 is indirectly driven by the guide rod 13 through the unidirectional bearing 12, the belt carrier 11 will be unable to feed the screws into the firing positing. When the guide rod 13 moves back to its start position, the belt carrier 11 will not be rotated due to the unidirectional bearing 12, so that the screws 15 will still stay in original start position but not in the firing position. At this moment, the screws cannot be fired.
Second, the belt carrier 11 is positioned by the elastic piece 14, however, the elastic piece 14 will be fatigued after a certain period of use, and consequently the belt carrier 11 may be over-rotated since it cannot be positioned precisely by the elastic piece. As a result, the screws 15 cannot be desirably fed into the firing position.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.